RefBase subclasses can now decide how they want to be destroyed.

This adds a destroy() virtual on RefBase which
sublasses can implement. destroy() is called
in lieu of the destructor whenthe last strong
ref goes away.

Bug: 4483050
Change-Id: I8cbf6044a6fd3f01043a45592b5a60fa1e5fade2

2 files changed, 17 insertions, 4 deletions

diff --git a/include/utils/RefBase.h b/include/utils/RefBase.h
index c24c0dbcb2..1b4a310008 100644
--- a/include/utils/RefBase.h
+++ b/include/utils/RefBase.h
@@ -115,7 +115,14 @@ public:
 protected:
                             RefBase();
     virtual                 ~RefBase();
-    
+
+    // called when the last reference goes away. this is responsible for
+    // calling the destructor. The default implementation just does
+    // "delete this;".
+    // Make sure to never acquire a strong reference from this function. The
+    // same restrictions than for destructors apply.
+    virtual void            destroy() const;
+
     //! Flags for extendObjectLifetime()
     enum {
         OBJECT_LIFETIME_WEAK    = 0x0001,
diff --git a/libs/utils/RefBase.cpp b/libs/utils/RefBase.cpp
index 0bd1af4ebf..c68e32a0df 100644
--- a/libs/utils/RefBase.cpp
+++ b/libs/utils/RefBase.cpp
@@ -298,6 +298,10 @@ void RefBase::incStrong(const void* id) const
     const_cast<RefBase*>(this)->onFirstRef();
 }
 
+void RefBase::destroy() const {
+    delete this;
+}
+
 void RefBase::decStrong(const void* id) const
 {
     weakref_impl* const refs = mRefs;
@@ -310,7 +314,7 @@ void RefBase::decStrong(const void* id) const
     if (c == 1) {
         const_cast<RefBase*>(this)->onLastStrongRef(id);
         if ((refs->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
-            delete this;
+            destroy();
         }
     }
     refs->removeWeakRef(id);
@@ -370,7 +374,8 @@ void RefBase::weakref_type::decWeak(const void* id)
     
     if ((impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
         if (impl->mStrong == INITIAL_STRONG_VALUE)
-            delete impl->mBase;
+            if (impl->mBase)
+                impl->mBase->destroy();
         else {
 //            LOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
             delete impl;
@@ -378,7 +383,8 @@ void RefBase::weakref_type::decWeak(const void* id)
     } else {
         impl->mBase->onLastWeakRef(id);
         if ((impl->mFlags&OBJECT_LIFETIME_FOREVER) != OBJECT_LIFETIME_FOREVER) {
-            delete impl->mBase;
+            if (impl->mBase)
+                impl->mBase->destroy();
         }
     }
 }